Research Notes:
The Oxford DNB provides a biography of Isabel de Warenne. [1]
[1] John A. Nichols, "Warenne, Isabel de [married name Isabel d'Aubigny], countess of Arundel (1226x30-1282)," Oxford Dictionary of National Biography (Oxford University Press, 2004, online edition), [Oxford_Dictionary_National_Biography], [OxfordDNB(UM)].